<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>sessionStorage</title>
</head>
<body>
  <h2>sessionStorage</h2>
  <button onclick="saveData()">点我保存一个数据</button>
  <button onclick="readData()">点我读取一个数据</button>
  <button onclick="deleteData()">点我删除一个数据</button>
  <button onclick="deleteAllData()">点我清空数据</button>
  <script>
    let p = {name: '张三', age: 18}

    function saveData() {
      sessionStorage.setItem('msg', 'hello!')
      sessionStorage.setItem('msg2', 666)
      sessionStorage.setItem('person', JSON.stringify(p))
    }

    function readData() {
      console.log(sessionStorage.getItem('msg'))
      console.log(sessionStorage.getItem('msg2'))
      console.log(JSON.parse(sessionStorage.getItem('person')))

      console.log(JSON.parse(sessionStorage.getItem('person2'))) // null
      console.log(sessionStorage.getItem('msg3')) // null 读不出来数据都是null
      
    }

    function deleteData() {
      sessionStorage.removeItem('msg2')
    }

    function deleteAllData() {  
      sessionStorage.clear()
    }

  </script>
</body>
</html>